Re: [RFC 1/7] xhci: Fix LPM disable/enable during device reset.
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On Thu, 5 Jul 2012, Sarah Sharp wrote: > The USB 3.0 specification says that sending a Set Feature or Clear > Feature for U1/U2 Enable is not a valid request when the device is in > the Default or Addressed state. It is only valid when the device is in > the Configured state. > > The original LPM patch attempted to disable LPM after the device had > been reset by hub_port_init(), before it had the configuration > reinstalled. The TI hub I tested with did not fail the Clear Feature > U1/U2 Enable request that khubd sent while it was in the addressed > state, which is why I didn't catch it. > > Move the LPM disable before the device reset, so that we can send the > Clear Feature U1/U2 Enable successfully, and balance the LPM disable > count. > > Also delete any calls to usb_enable_lpm() on error paths that lead to > re-enumeration. The calls will fail because the device isn't > configured, and it's not useful to balance the LPM disable count because > the usb_device is about to be destroyed before re-enumeration. > > Fix the early exit path ("done" label) to call usb_enable_lpm() to > balance the LPM disable count. > > Note that calling usb_reset_and_verify_device() with an unconfigured > device may fail on the first call to usb_disable_lpm(). That's because > the LPM disable count is initialized to 0 (LPM enabled), and > usb_disable_lpm() will attempt to send a Clear Feature U1/U2 request to > a device in the Addressed state. The next patch will fix that. > > This commit should be backported to kernels as old as 3.5, that contain > the commit 8306095fd2c1100e8244c09bf560f97aca5a311d "USB: Disable USB > 3.0 LPM in critical sections." What about the LPM-related calls in usb_port_suspend and usb_port_resume? A device can be suspended even when it's not configured. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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